1. Field of the Invention
The present invention relates to a lens apparatus and an optical apparatus including the same.
2. Description of the Related Art
In a conventionally known configuration, a cam barrel and a straight guiding barrel are relatively moved to move a lens holding barrel in an optical axis direction. Specifically, Japanese Patent Laid-open No. 2009-42345 discloses a configuration including a cam barrel in which cam groove portions are formed at multiple circumferential positions, a straight guiding barrel in which straight groove portions are formed at multiple circumferential positions and a straight movable barrel holding a lens. In this configuration, cam followers are mounted to the straight movable barrel; each cam follower includes a roller portion (cylindrical portion) engaging with the cam groove portion of the cam barrel and a key portion engaging with a straight groove portion of the straight guiding barrel, and thereby the straight movable barrel is moved in the optical axis direction.
In Japanese Patent Laid-open No. 2009-42345, the straight movable barrel is disposed outside the cam barrel and the straight guiding barrel, and each cam follower is pulled by a screw toward the straight movable barrel to be fixed thereto. Such a configuration causes decentering and tilt in which the lens held by the straight movable barrel serving as a lens holding barrel is shifted from an ideal position on the optical axis because of manufacturing accuracy (tolerance) of each component, thereby degrading optical performance.
The shape of the cam groove portion formed in the cam barrel is set depending on a movement locus of a lens unit for zooming or focusing. Some lens configurations have a so-called U-turn cam in which a positive and negative sign of an angle (intersection angle) formed by the cam groove portion with the straight groove portion changes between a wide-angle side and a telephoto side or between an infinity side and a close side.
For example, an angular position tolerance (equal division difference) of the cam groove portions in the cam barrel and of the straight groove portions in the straight guiding barrel causes engagement of the cam followers with the cam groove and straight groove portions at positions shifted from ideal engagement positions, thereby causing tilt and decentering of the straight movable barrel. In particular, in the straight movable barrel moved by the above-mentioned U-turn cam, the intersection angle inverts between the wide-angle side and the telephoto side or between the infinity side and the close side, so that the direction of the tilt also inverts therebetween, resulting in a larger change amount of the tilt.
For such a lens unit affecting degradation of optical performance, decentering adjustment and tilt adjustment of the lens unit are typically performed taking the optical performance as an evaluation item. In the case of including the U-turn cam, however, when the decentering adjustment and the tilt adjustment of the lens unit are performed to improve optical performance at, for example, the telephoto side or the infinity side, the optical performance can be improved at the telephoto side or the infinity side, but an opposite tilt is caused at the wide-angle side or the close side. This results in greater degradation in optical performance than that caused in a case of using a normal cam groove portion which is not the U-turn cam.
Thus, in the case of including the U-turn cam, the change in the intersection angle due to the U-turn cam in adjusting the optical performance by adjustment of any one of the lens units or all of the lens units causes a significant degradation in the optical performance.
Therefore, for example, correcting variation due to the equal division difference of the straight groove portions and the cam groove portions enables suppressing the change in tilt due to the U-turn cam. For example, as a well-known technique, decentering the roller portion (cylindrical portion) engaging with the cam groove portion of the cam barrel with respect to the key portion engaging with the straight groove portion of the straight guiding barrel enables adjusting a circumferential shift caused by the equal division difference.
Japanese Patent Laid-open No. 2010-197698 discloses an easy-to-assemble lens barrel configuration with cam followers each including a first cylindrical portion (engaging with a cam groove portion and a straight guiding groove portion) and a second cylindrical portion (engaging with a cam follower position controlling portion of a straight movable barrel).
In the straight movable barrel as the lens holding barrel disclosed in Japanese Patent Laid-open No. 2009-42345, however, the cam follower is pulled by the screw toward the straight movable barrel to be fixed thereto, which makes it difficult to adjust the cam follower and thus makes it difficult to adjust the equal division difference.
Moreover, the configuration disclosed in Japanese Patent Laid-open No. 2010-197698 allows suppressing the change in tilt due to assembly variation, but does not allow suppressing the change in tilt due to component variation.